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23 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Sideseadmed,

probleemid ja lahendused (2)

Avo Ots

13. märts 2006

R
eference model

Application

Transport

Network

Data Link

Physical

Medium

Data Link

Physical

Application

Transport

Network

Data Link

Physical

Data Link

Physical

Network

Network

Radio

Mobile devices

performance

Pager



receive only



tiny displays



simple text


messages

Mobile phones



voice, data



simple graphical displays

PDA



simpler graphical displays



character recognition



simplified WWW

Palmtop



tiny keyboard



simple versions


of standard applications

Laptop



fully functional



standard applications

Sensors, and

embedded

controllers

Overlay Networks
-

the global goal

regional

metropolitan area

campus
-
based

in
-
house

vertical

handover

horizontal

handover

integration of heterogeneous fixed and

mobile networks with varying

transmission characteristics

Typical application: road traffic

UMTS, WLAN,

DAB, GSM,

cdma2000, TETRA, ...

Personal Travel Assistant,

DAB, PDA, laptop,

GSM, UMTS, WLAN,

Bluetooth, ...

_

Radio relay (mesh) networks are gathering momentum


many are based on 802.11 radio technology and therefore have a low cost base


back
-
haul is considerably less than for conventional cellular

WLAN access points

Fixed ‘seed’ nodes

User terminals

Infrastructure mesh:

Relaying between access points only
These links are static or slowly changing

Mobile mesh:

Relaying between all devices
with fast dynamic routing

Ad
-
hock and sensor networks

DECT


DECT (Digital European Cordless Telephone) standardized by ETSI
(ETS 300.175
-
x) for cordless telephones


standard describes air interface between base
-
station and mobile
phone


DECT has been renamed for international marketing reasons into
„Digital Enhanced Cordless Telecommunication“


Characteristics


frequency: 1880
-
1990 MHz


channels: 120 full duplex


duplex mechanism: TDD (Time Division Duplex) with 10 ms
frame length


multplexing scheme: FDMA with 10 carrier frequencies,

TDMA with 2x 12 slots


modulation: digital, Gaußian Minimum Shift Key (GMSK)


power: 10 mW average (max. 250 mW)


range: ca 50 m in buildings, 300 m open space

DECT system architecture reference
model

global

network

local

network

local

network

FT

FT

PT

PA

PT

PA

VDB

HDB

D
1

D
2

D
3

D
4

physical layer

medium access control

data link

control

data link

control

network

layer

OSI layer 1

OSI layer 2

OSI layer 3

U
-
Plane

C
-
Plane

signaling,

interworking

application

processes

DECT reference model


close to the OSI
reference model


management
plane over all
layers


several services
in C(ontrol)
-

and
U(ser)
-
plane

management

DECT layers I


Physical layer


modulation/demodulation


generation of the physical channel structure with a guaranteed
throughput


controlling of radio transmission


channel assignment on request of the MAC layer


detection of incoming signals


sender/receiver synchronization


collecting status information for the management plane


MAC layer


maintaining basic services, activating/deactivating physical
channels


multiplexing of logical channels


e.g., C: signaling, I: user data, P: paging, Q: broadcast


segmentation/reassembly


error control/error correction


DECT time multiplex frame

slot

sync

A field

DATA

DATA

64

C

16

DATA

64

C

16

DATA

64

C

16

DATA

64

C

16

B field

D field

1 frame = 10 ms

12 down slots

12 up slots

0

419

0

31

0

387

0

63

0

319

protected

mode

unprotected

mode

simplex bearer

25.6 kbit/s

32 kbit/s

420 bit + 52 µs guard time („60 bit“)

in 0.4167 ms

guard

X field

0

3

A: network control

B: user data

X: transmission quality

DECT layers II


Data link control layer


creation and keeping up reliable connections between
the mobile terminal and basestation


two DLC protocols for the control plane (C
-
Plane)


connectionless broadcast service:

paging functionality


Lc+LAPC protocol:

in
-
call signaling (similar to LAPD within ISDN), adapted to
the underlying MAC service


several services specified for the user plane (U
-
Plane)


null
-
service: offers unmodified MAC services


frame relay: simple packet transmission


frame switching: time
-
bounded packet transmission


error correcting transmission: uses FEC, for delay critical,
time
-
bounded services


bandwidth adaptive transmission


„Escape“ service: for further enhancements of the standard

DECT layers III


Network layer


similar to ISDN (Q.931) and GSM (04.08)


offers services to request, check, reserve, control, and
release resources at the basestation and mobile terminal


resources


necessary for a wireless connection


necessary for the connection of the DECT system to the fixed
network


main tasks


call control: setup, release, negotiation, control


call independent services: call forwarding, accounting, call
redirecting


mobility management: identity management, authentication,
management of the location register

Analüüsitav
setup

http://www.mmwave.com/pdf/basestation_vari_da
tasheet.pdf